rextio-lsp 0.1.0

Language Server for the Rextio native-promotion tooling contract.

rextio-lsp

Language Server for Rextio — native-promotion routes and guidance in your editor.

A Python (pygls) LSP server that runs inside your project's environment, imports the Rextio analyzer in-process, and reports per-function execution routes (native-direct, native-plugin:<id>, native-shim, fallback-python, fallback-accelerated:numba, rejected:<RXT>) with actionable promotion guidance.

Designed to coexist

rextio-lsp registers only Rextio-semantic capabilities and stays out of everything else:

• Provides: diagnostics (source: "rextio", RXT/RXTP codes only, default Hint/Info severity), hover (route info + rejection and advisory guidance), code lens (per-function route badges), code actions (promotion quick fixes)
• Does not provide: completion, formatting, rename, definition, references, syntax/style linting — those remain with your existing Python LSP (Pylance/pyright, ruff, …)
• Activates only when rextio.toml exists in the workspace; silent no-op when Rextio isn't installed in the project environment

Features

M1

• Whole-project rextio check on open/save (debounced), published as source: "rextio" diagnostics
• Severity is capped: rejection codes → Warning, informational codes (RXT075/080/090/091) → Hint, everything else → Information (never Error)
• Hover on a function definition line shows its route, native status, and rejection guidance (from the capability manifest)
• Acquisition prefers importing the project's own rextio in-process, falling back to a discovered rextio binary subprocess
• Unsupported contract major → degraded (generic) diagnostics without guidance enrichment

M2

• initializationOptions contract (see below): toggle code lens, pin the interpreter used for binary discovery
• Code lens: one Rextio: <route> lens per analyzed function, carrying the informational rextio.showRouteInfo command with [qualname] (registered only when codeLens.enable is true)
• Code actions (quickfix): on a rejected function that carries an explicit @rextio.native marker, offer "Rextio: keep on Python fallback (@rextio.exempt)" — rewrites the decorator to @rextio.exempt (indentation preserved)
• Hover also surfaces an Advisory section for informational codes present on the function, not just rejections
• Watches **/rextio.toml; on change, drops the project's cached capability manifest and re-analyzes open documents
• Real diagnostic spans when the contract provides end_line/end_column (else a zero-width range)
• Latency instrumentation: each whole-project check is logged via window/logMessage (Info when > 2.0s, else Log)

initializationOptions

The server reads the following shape (all keys optional; defaults shown):

{
  "codeLens": { "enable": true },
  "interpreter": { "path": null }
}

• codeLens.enable — when false, the code lens capability is not advertised at all.
• interpreter.path — path to the project's Python interpreter. When set, it is consulted first when locating the rextio binary for the subprocess fallback (before the project .venv/venv and PATH).

Install

Install into the project environment so the server stays in version lock-step with the project's rextio and its plugins:

pip install rextio-lsp

The server speaks LSP over stdio via the rextio-lsp console script (equivalently python -m rextio_lsp).

Editor setup

Neovim (nvim-lspconfig, manual command)

rextio-lsp is not yet a built-in lspconfig server, so register it manually:

local configs = require("lspconfig.configs")
local lspconfig = require("lspconfig")

if not configs.rextio_lsp then
  configs.rextio_lsp = {
    default_config = {
      -- run the server from the project's own environment
      cmd = { ".venv/bin/rextio-lsp" },
      filetypes = { "python" },
      root_dir = lspconfig.util.root_pattern("rextio.toml"),
      init_options = {
        codeLens = { enable = true },
        interpreter = { path = vim.fn.getcwd() .. "/.venv/bin/python" },
      },
    },
  }
end

lspconfig.rextio_lsp.setup({})

Enable code lens rendering with vim.lsp.codelens.refresh() (e.g. on BufEnter/CursorHold) and :lua vim.lsp.codelens.display().

Generic stdio client

Any LSP client that launches a stdio subprocess works. The essentials:

• command: rextio-lsp (or python -m rextio_lsp) from the project environment
• transport: stdio
• languages: python
• root: nearest directory containing rextio.toml
• initializationOptions: the shape documented above

Development

pip install -e '.[dev]'
ruff check src tests
mypy
pytest -q

Integration tests marked needs_rextio are auto-skipped when rextio is not importable.

License

MIT